Hydraulic system for power shears and like machines



Jan. 18, 1955 K. Y. MESSICK 2,699,649

HYDRAULIC SYSTEM FOR POWER SHEARS AND LIKE MACHINES Filed July 15, 1949INVENTOR Jf'r wan X Mess/ck ATTORNEYS United States Patent Ofifice2,699,649 Patented Jan. 18, 1955 HYDRAULIC SYSTEM FOR POWER SHEARS ANDLIKE MACHINES Kirwan Y. Messick, Arlington, Va. Application July 15,1949, Serial No. 104,910

Claims. (Cl. 60--51) This invention relates to hydraulically operatedpower shears and like machines. Devices of this character are frequentlyrequired to work upon heavy metal, such for example as the shearing ofsteel plates of considerable thickness and it is of importance that theybe capable of exerting very great power and that the work be firmly heldin place during the cutting operation. It is a primary object of theinvention to provide a plurality of hydraulic work clamping plungersarranged in a free and unobstructed fluid supply circuit with the mainoperating cylinders of a hydraulic shear in such way that the pressureexerted upon the work clamping plungers is always directly proportionedto the power required to shear the particular piece of material beingoperated upon.

It is a further object to so arrange the fluid supply circuit of themain power cylinders and the work clamp that said circuit will always befilled with pressure fluid and upon the closing of a valve in thecircuit to interrupt the oil flow therein pressure will immediatelybegin to be imposed upon the main cylinders and pistons and the workclamping pistons, whereby the work clamping pistons having lessresistance to their movement than the main pistons will quickly andquietly move to work clamping position, the main pistons moving onlyafter the pressure builds up to a point to cause them to move to do thework at hand.

It is a further object of the invention to provide double acting mainpower cylinders and pistons in a circuit of the above describedcharacterand in which the pressure fluid on one side of the main pistonsacts to effect the out while at the same time the pressure fluid uponthe other side of the main pistons is ejected into an accumulatoragainst the resistance of a compressible fluid to there store uppressure to effect the return stroke of the ram or knife after thecutting stroke is completed.

Further objects and advantages of the invention will be set forth in thedetailed description which follows.

In the accompanying drawing:

Fig. 1 is a diagrammatic view illustrating the hydraulic circuit of themachine;

Fig. 2 is a view partly in section and partly in side elevation showingthe construction of the work clamping cylinders and plungers; and

Fig. 3 is a transverse vertical sectional view through a hydraulic presshaving the invention applied thereto.

Like numerals designate corresponding parts in all of the figures of thedrawing.

In the drawing 5 designates the work table of a hydraulic shear. A fixedknife 6 cooperates with a movable knife 7, the latter being carried by avertically reciproca tory head or ram 8. vertical reciprocatory movementis imparted to head 8 by links 9, crank arms 10 on oscillatory torquetube 11 and crank arms 12, from the piston rods 13 of hydrauliccylinders 14 there being one of these cylinders at each end of the shearand said cylinders acting in unison upon the head through the medium ofthe heavy connecting torque tube 11.

A fluid pressure circuit line 15 is connected to the outer or workperforming end of the cylinders 14 and this circuit includes a fixedmanifold may be a part of a heavy face frame.

A port 18 leads through the manifold and is a part of the fluid circuit.Small plate 17 of the machine In accordance with known practice,

16 that is carried by and manifold are in communication, at their upperends with port 18. Springs 20 within the cylinders bear between collars21 which are threaded into the lower ends of the cylinders and collars22 of ring like form that are engaged in annular grooves 23 of workclamping plungers 24. The plungers are moved into engagement with thework to be held by the action of pressure fluid, such as oil, whichenters cylinders 19 from port 18 of the manifold and they are returnedto elevated positions by said springs. An electric motor 25 drives anoil pump 26 that is mounted upon a wall 27 of an oil tank or reservoir28. Oil is delivered directly from the pump through branch line 15a toline 15 and port 18 of the manifold. An oil return line 15b leads fromline 15 back to the tank, the said tank being under atmosphericpressure.

Located in the oil return line 15b is a conventional electricallyoperated shut off valve 29 the actuating solenoid casing of which isindicated at 30. A conventional pressure relief valve 31 is located inline 15a within the tank and guards against an excess of pressure beingbuilt up within the line 15 and associated elements.

oil pressure line 32 is connected to the outer or non-working endportions 14a of the cylinders 14 and when the pistons move outwardlythey not only actuate the ram as described to effect a shearing actionbut they also expel oil from the outer ends of said cylinders into andthrough line 32 to an accumulator 33. Accumulators of this type are wellknown. They comprise a heavy and strong shell 34, containing aninflatable bladder 35. By inflating this bladder with compressible fluidsuch as air, to a determined pressure, the forcing of the oil fromcylinders 14 into said shell between the shell and exterior of thebladder, will further compress the air or like compressible fluid in thebladder and thereby store up such power that the return stroke of theram and pistons on piston rods 13 may be effected by such stored powerin the accumulator whenever the opening of valve 29 releases thepressure in line 15. The operation of the device is as follows.

When shearing is to be done the motor and pump are started and they runcontinuously. The entire freely connected, unobstructed circuit,represented by the lower ends of cylinders 14, the interiors ofcylinders 19, conduit 18 and lines 15, 15a and 15b, is filled with oilwhich is being circulated by the pump from and to reservoir 28. When itis desired to effect the cutting or shearing of a sheet of metal saidsheet is placed on the work table in proper position and the operatorpresses a pedal (not shown) to energize the solenoid shut off valve, toclose the same. This causes a pressure rise in the oil lines, suchpressure rise being immediately and equally imposed upon the workclamping plungers and the underside of the pistons in cylinders 14.Since the return springs of the work clamping plungers are merely strongenough to return the plungers to elevated position and since the forcerequired to start the ram on its downward stroke against the accumulatedpressure in accumulator 33 is far greater than the force required to setthe work clamping plungers 24 down upon the work to be held, it followsthat just as soon as valve 29 closes these plungers move quietly andwithout a striking blow down upon the work and that the pressure uponthese plungers builds up until it equals the pressure required to movethe pistons outwardly in cylinders 14. This pressure is: the pressurerequired to overcome the power stored in the accumulator plus thepressure required to shear metal of the particular nature and thicknessthat is being cut. Thus the pressure on the clamping plungers varies indirect proportion to the work being done. The result of the arrangementdescribed is that the shear operates at the most economical speed. Thisis because no more pressure has to be built up on the work clampingplungers than is necessary, all excess pressure being expended in usefulwork in the main cylinders. Therefore the expression freely open,unobstructed circuit, as used in the claims is to be understood to meana circuit free of valves or other impediments designed to create apressure on the work clamping cylinders ahead of the time that pressurestarts to build up in the main cylinders 14. By permitting flow of oilto the main cylinders as soon as any pressure is created anywhere thebuilding up of the pressure on the clamping pistons is less abrupt thanif all available pressure were first imposed on the work clampingpistons. One of the important advantages of this device is that while it1s adapted to do quite heavy work it is also very speedy 1n action. Thisarises largely from the fact that I utilize the time employed by theoperator in positioning the work beneath theclamps, to set the pressurefluid in motion by the continuously moving pump. When the solenoid valve29 snaps shut the kinetic energy of the flowing oil is quickly deliveredto the clamps and power cylinders. Thus I am able to cause my shear tomake many strokes per minute with consequent economy in operation.Further itis 'to be'noted that all of the parts which I employ are ofvery simple construction. Thus I am able to produce a shear much moreeconomically than has heretofore been done in presses of like capacity.

This freely open unobstructed circuit effects a saving A of time in thatwhile the Work clamping plungers are moving to engage the work thepressure is being built up in the much larger area main cylinders 14 sothat movement of the ram on its cutting stroke follows almostimmediately after the clamping of the work.

Air under pressure may be admitted to bladder 35 through air inlet 35aand by the mere adjustment of this air pressure the power to return theram to elevated positionand the pressure to be created in the operatingfluid circuit lines 15 etc. may be easily adjusted and controlled.

The setting of the clamping plungers gently down upon the work renderstheir operation almost noiseless and it avoids damage to the work suchas might result from too forcible movement of said plungers. This damageis likely to occur when thin stock or soft metals such as brass, copper,aluminum, etc. are being worked upon. Further the abolition of excessivenoise is of itself highly desirable. The noise made by some types ofhydraulic shears, brakes and like presses, equipped with hydraulic workclamping plungers is exceedingly great, being of the order of that whichwould be created by a number of hammers forcibly striking the heavymetal work table of the shear. With a number of these machines inoperation the resultant din is terrific and imposes severe nerve strainsupon workmen forced to endure it over long periods of time.

Efficiency experts and psychologists are agreed that the creation ofpleasant working conditions increases the efliciency and health of theindividual workers. This invention will contribute to that'result.

While the invention is especially useful in power shears it may also beutilized in hydraulic brakes and other types of machines where work isto be clamped ahead of the hydraulic operation of work performingmembers.

A pressure relief valve 37 in line 38 prevents leakage past the pistonsfrom building up an excess of pressure in the accumulator.

While I have stated that the cylinders 14 are double acting the two endsof the cylinders each perform their separate functions and the provisionof two single acting cylinders would be the equivalent thereof. In thatcase one single acting cylinder would move the ram and the ram wouldmove the plunger of another single acting cylinder to compress oil intothe accumulator. The continuing flow of oil through a completely opencircuit that is unobstructed by valve casings or dead ends 'insure'sthat any air in the oil will be immediately returned to the tanks. Thusit is not necessary to provide a special air bleed .valve. 7 ,It is tobe understood thatthe invention is not limited tothe preciseconstruction set forth but that it includes within. its purview whateverchanges fairly come within either the terms or the spirit of theappended claims.

WhatTclaim is: v

, l. A fluidv pressure system for use in conjunction with machines ofthe type performing such heavy duty asto require power means for holdingwork during the opera tion of the machines thereon and which machinescomprise a reciprocatory working head, a pair of primary hydraulic powercylinders and pistons therein for moving said head upon its workingstroke and a plurality of fluid pressure o erated work holding. clampscomprising secondary, -cvlinders and pistons therein. the pistons of allof said clamps being operable simultaneously under the same degree ofpressure and at a materially lower pressure than that required toactuate the pistons of the primary power cylinder; said systemconsisting of a freely open and unobstructed circuit for pressure fluidin which the primary and secondary cylinders are included, saidsecondary cylinders being of uniform size and connected in parallel intosaid circuit to have their pistons all simultaneously and uniformlyactuated by said pressure fluid, said primary cylinders being likewisedisposed in parallel in the said circuit,.a continuously operating pumpin the circuit, for maintaining a continuous flow of pressure fluidthereth'roug'h from and back to said pump, and a shut off valve in thereturn line to the pump located at a point beyond all of said cylinders,the closing of which causes the pump pressure to first simultaneouslyactuate all of the more easily actuated secondary pistons and thereafterbuild up pressure in the primary cylinders to actuate the primary pistontherein.

2-. A- structure as recited inclaim 1 wherein the primary cylinders aredouble acting cylinders with the named circuit communicating with thespace at one side of the primary piston, a fluid pressure linecommunicating withthe space within the primary cylinder upon the otherside of theprimary piston, a fluid pressure accumulator to which thelast named fluid pressure line leads and pressure relief means forrelieving any excess pressure imposed upon the accumulator by highpressure fluid from the working side of the primary cylinder, passingthe piston therein.

3'. A structure as recited in claim 1 wherein the primary cylinders andtheir pistons are double acting with the space upon one side of theprimary pistons constituting the working end of the cylinder and towhich the said power fluid circuit is connected, a second fluid circuitconnected to the primary cylinders upon that side of the primary pistonsremote from the working end of the primary cylinders, a fluid pressurepower accumulator comprising a casing and an inflatable body therein andtowhich casing the last named fluid circuit is connected, means forinflating the inflatable body to a predetermined and set degree and asettable relief valve for relieving the pressure in the casing wheneverpressure from the power side of the primary pistons, passing saidprimary pistons, builds up-the pressure in the accumulator to a pointgreater than that for which the relief valve has been set.

4. A fluid pressure system for use in conjunction with work performingmachines of the type comprising a primary work performing, hydraulic,cylinder and piston, and a plurality of hydraulic secondary powercylinders and pistons which exercise a uniform and simultaneouspreparatory function for the action of the primary cylinder and piston,said secondary pistons all being operable under a same degree of lowerpressure than the primary piston, said system comprising a freely openand unobstructed circuit for pressure fluid flow in which circuit boththe primary and secondary cylinders and pistons are all included, acontinuously operating pump in the circuit for maintaining a continuousflow of pressure fluid therethrough from said pump and back to said pumpand a shut off valve in the return line to the pump located at a pointbeyond all of said cylinders, the closing of which causes the pumppressure to first simultaneously actuate all of the more easily.actuated secondary pistons and thereafter build up pressure in theprimary cylinder to actuate the primary piston therein. 7

v 5. A fluid pressure system for use in conjunction with machines of thetype performing such heavy duty as to require power means for holdingwork during the operation ofthe machines and which machines comprise areciprocatory working head, a primary hydraulic power cylinder andpiston therein acting to move said head upon its working stroke and aplurality of fluid pressure operated work holding clamps comprisingsecondary cylinders and pistons therein, the pistons of all of saidclamps being operable simultaneously under the same degree of pressureand at a materially lower pressure than that required to actuate thepiston of the primary power cylinder, said system consisting of a freelyopen and unobstructed circu'it for pressure fluid in which the primarycylinder and secondary cylinders are included, said secondary cylindersbeing of uniform sizeand connected in parallel into said circuit to havetheir pistons all simultaneously and uniformly actuated by said pressurefluid. said primary cylinder being likewise disposed inparallel in' saidcircuit with the secondary cylinders, a continuously operating pump inthe circuit, for maintaining a continuous flow of pressure fluidtherethrough from and back to said pump, and a shut 01f valve in thereturn line to the pump located at a point beyond all of said cylinders,the closing of which causes the pump pressure to first simultaneouslyactuate all of the more easily actuated secondary pistons and thereafterbuild up pressure in the primary cylinder to actuate the primary pistontherein.

References Cited in the file of this patent UNITED STATES PATENTSKennedy Apr. 30, 1889 Guild et al Sept. 13, 1898 Maxwell Aug. 31, 1909London Nov. 30, 1909 Riddle Apr. 7, 1942 Krerniller Mar. 11, 1947Sanders et al June 22, 1948 Poville July 13, 1948 Yates Aug. 3, 1948

